Apparatus for and method of controlling fuel injection of internal combustion engine

ABSTRACT

There is provided a configuration in which a cylinder which is in an inlet stroke when an internal combustion engine is in a stop (automatic stop) state is determined and stored, and when starting the engine upon detection of a start request, the fuel injection of an initial cycle to the cylinder, which has been determined as having been stopped in the inlet stroke when the engine was in the stop state before starting, is split into a plurality if injections at least including an injection before engine rotation, to thereby perform injections. As a result, startability is improved while suppressing pre-ignition at the time of starting.

1. FIELD OF THE INVENTION

The present invention relates to an apparatus for and a method ofcontrolling fuel injection of an internal combustion engine, inparticular, to fuel injection control performed when restarting aninternal combustion engine which has been automatically stopped or whenstarting it in a warm-up completion state.

2. DESCRIPTION OF RELATED ART

Japanese Laid-open (Kokai) Patent Application Publication No.2008-215192 discloses a fuel injection control apparatus of an internalcombustion engine in which, at the time of restarting after completionof a warm-up operation (when restarting from an idle stop state forexample) fuel injection is executed before starting (cranking), and thefuel injection amount during starting after engine rotation isreduction-corrected.

The above disclosed apparatus is of a configuration in which aninjection amount required for starting is injected all at once in astate in which the engine is stopped before starting (before enginerotation).

However, in such a configuration in which the entire amount is injectedat once, the penetration force (penetration) of fuel spray is high andinjection is performed in a state in which there is no intake air flowtowards the interior of a cylinder. Consequently, the amount of adhesionon the inlet air passage wall surface becomes high and the evaporationrate within the inlet air passage becomes reduced.

Therefore there is a possibility that the effect of cooling the interiorof the inlet air passage by the latent heat of vaporization of the fuelspray may be reduced, and intake air of a comparatively high temperaturemay be introduced into a cylinder at the time of restarting the engine,consequently causing an auto-igniting phenomenon (pre-ignition) tooccur.

SUMMARY OF THE INVENTION

Consequently, an object of the present invention is to suppresspre-ignition when restarting an internal combustion engine which hasbeen automatically stopped, or when starting it in a warm-up completionstate, and thereby improve startability.

In order to achieve the above object, the present invention is

an apparatus for and a method of controlling fuel injection of aninternal combustion engine for a vehicle in which fuel is injected froma fuel injection valve to an inlet port of each cylinder, wherein:

A. a cylinder which has been stopped in an inlet stroke is determinedwhen the internal combustion engine is stopped;

B. a start request of the internal combustion engine is detected; and

C. when starting the engine based on the start request, fuel injectionin the initial cycle to the cylinder, which was stopped in the inletstroke, is split into a plurality of injections at least including aninjection before engine rotation, to thereby perform injections.

The other objects and features of this invention will become understoodfrom the following description with reference to the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram of an internal combustion engine for avehicle to which the present invention is applied.

FIG. 2A is a time chart of a first embodiment, and FIG. 2B is a timechart of a second embodiment.

FIG. 3A is a time chart of a third embodiment, and FIG. 3B is a timechart of a fourth embodiment.

FIG. 4A is a time chart of a fifth embodiment, and FIG. 4B is a timechart of a sixth embodiment.

FIG. 5A is a flow chart of the first embodiment.

FIG. 5B is a flow chart of the second and fourth embodiments.

FIG. 5C is a flow chart of the third and fifth embodiments.

FIG. 5D is a flow chart of the sixth embodiment.

FIG. 5E is a flow chart of a seventh embodiment.

FIG. 6 is a time chart of an example of the second embodiment.

FIG. 7 is a time chart of another example of the second embodiment.

FIG. 8 is a flow chart of valve closing timing control of an inlet valvewhen the internal combustion engine is automatically stopped.

FIG. 9 is a time chart of valve closing timing control of the same inletvalve.

FIG. 10A is an enlarged view of a peripheral part of an injection nozzlehole of a spray impingement type fuel injection valve, FIG. 10B is across-sectional view showing a nozzle plate in FIG. 10A alone, FIG. 10Cis a plan view showing the nozzle plate alone, FIG. 10D is anenlargement view of a relevant part showing the respective nozzle holepairs in FIG. 10C being operated in a fuel injection operation, and FIG.10E is an enlarged cross-sectional view of each nozzle hole, whichconstitutes the nozzle hole pair, seen from the direction illustratedwith arrows VI-VI in FIG. 10D.

FIG. 11 is a flow chart showing a relevant part of fuel pressure raisingcontrol at the time of restarting.

DESCRIPTION OF PREFERRED EMBODIMENTS

Hereunder, embodiments of the present invention are described, withreference to the accompanying drawings.

FIG. 1 is a configuration diagram of an internal combustion engine for avehicle to which the present invention is applied. On an inlet pipe 102of an internal combustion engine 101 there is disposed an electronicallycontrolled throttle 104 which drives a throttle valve 103 b open andclose, with a throttle motor 103 a. Air is sucked into a combustionchamber 106 via electronically controlled throttle 104 and an inletvalve 105.

Exhaust gas is discharged from combustion chamber 106 through an exhaustvalve 107, is purified in a front catalyst 108 and a rear catalyst 109,and is then discharged into the atmosphere.

Exhaust valve 107 is driven to open or close by a cam 111 supported onan exhaust side cam shaft 110, while maintaining a constant lift amountand a working angle (crank angle from open to close). On the other hand,regarding inlet valve 105, lift amount and working angle, that is, valveopening, can be continuously changed by a variable valve lift mechanism112. The lift amount and working angle can be simultaneously changed sothat when the characteristic of one is determined, the characteristic ofthe other is also determined.

On both end sections of an inlet side cam shaft, there are provided avariable valve timing mechanism 201 and an inlet side cam angle sensor202. Variable valve timing mechanism 201 includes a mechanism whichcontinuously performs variable control of rotational phase differencebetween the crank shaft and the inlet side cam shaft to thereby advanceor retard the valve timing (valve opening/closing timing) of inlet valve105. Inlet side cam angle sensor 202 detects a rotational position ofthe inlet side cam shaft.

An engine control electronic control unit (EECU) 114 controlselectrically controlled throttle 104 and variable valve lift mechanism112 depending on the opening of an acceleration pedal detected by anaccelerator opening sensor APS 116. With this control, by using theopening of throttle valve 103 b and the opening characteristic of inletvalve 105 it is possible to obtain a target intake air amount whichcorresponds to an accelerator opening ACC. Accelerator opening sensorAPS 116 has a built-in idle switch 116 a which detects an acceleratoropening equal to or less than a predetermined opening, as an idle state(turned ON).

EECU 114 receives signal inputs from each of the following sensors aswell as from accelerator opening sensor APS 116 and inlet side cam anglesensor 202. A rotation angle sensor 127 detects a rotational angle of acontrol shaft which is driven by an electric motor serving as anactuator of variable valve lift mechanism 112. Detection of therotational angle of the control shaft corresponds to detection of thelift amount and working angle of the inlet valve. An airflow meter 115detects an intake air amount Q of engine 101. A crank angle sensor 117extracts engine rotation signals (a signal output at every unit angleand a cylinder determination signal output at every stroke phasedifference) from the crank shaft. A throttle sensor 118 detects anopening TVO of throttle valve 103 b. A water temperature sensor 119detects a cooling water temperature Tw of engine 101. A vehicletraveling speed sensor 125 detects a vehicle traveling speed, and abrake sensor 126 detects an operating state (ON and OFF) of a brake.

Moreover, on an inlet port 130 on the upstream side of inlet valve 105of each of the cylinders, there is provided an electromagnetic type fuelinjection valve 131. Fuel injection valve 131 injects fuel, which hasbeen adjusted to a predetermined pressure, toward inlet valve 105, whenit is driven open by an injection pulse signal from EECU 114.

On the other hand, an idle-stop control electronic control unit (ISECU)120 performs idle stop control which stops fuel injection of theinternal combustion engine to thereby automatically stop its operationwhen the vehicle is stopped in an idle state (in a state in which theaccelerator pedal is released), and performs control to restart theinternal combustion engine when the operation has been automaticallystopped and an occurrence of a restart request has been detected.

Moreover, as vehicle power supplies, there are provided a lead battery121 and a lithium-ion battery 122. At restart after the internalcombustion engine is automatically stopped, a starter 123 is activatedusing high-voltage lithium-ion battery 122. When starting the engine bymanually operating a starter switch, low-voltage lead battery 121 isused to activate starter 123. ISECU 120 performs switching control of aswitching relay 124 to thereby switch the battery to be used. ISECU 120also performs control for maintaining the state of charge (SOC), thevoltage, and the like of lithium-ion battery 122.

From EECU 114, ISECU 120 receives signals from sensors required forperforming these controls such as idle switch 116 a, vehicle travelingspeed sensor 125, brake sensor 126, and the like, and it sends commandsignals for automatically stopping and restarting the engine to EECU114, so as perform these controls.

EECU 114 determines and stores the cylinder which is in an inlet strokewhen the internal combustion engine is automatically stopped (thecylinder in which a piston therein is stopped at an inlet strokeposition. Hereunder, referred to as inlet stroke stopped cylinder), andthe crank angle position of the inlet stroke stopped cylinder. Whenstarting the engine based on the start request, fuel injection in theinitial cycle with respect to the inlet stroke stopped cylinder is splitinto a plurality of injections at least including an injection performedbefore engine rotation, to thereby perform injections.

In this embodiment, there are provided two ECU units namely EECU 114 andISECU 120, and control functions are assigned thereto, and consequentlythe size of individual ECU units can be made compact, thereby improvingthe degree of freedom in the layout thereof. However, of course theconfiguration may also be provided so as to perform both controls on asingle ECU unit.

Next, there are described respective embodiments of fuel injectioncontrol, according to the present invention, for when restarting basedon a start request after automatic stop. In the respective embodiments,in addition to a start request after automatic stop, a restart requestafter completion of a warm-up operation (an operation of a startingswitch such as an ignition switch and a start switch performed by adriver) may be judged, and fuel injection control in restarting may beexecuted according to the respective embodiments.

When a predetermined idle stop condition (automatic stop condition) issatisfied, fuel injection of the internal combustion engine is stoppedand the engine operation is automatically stopped. The predeterminedidle stop condition includes a moment when depression of a brake pedalis detected in a vehicle stop state for example.

The vehicle stop state may be determined when a detection value VSPdetected by the vehicle traveling speed sensor 125 is 0, or it is lessthan or equal to a predetermined value for determining a vehicle stop.

Moreover, detection of depression of the brake pedal may be determinedas a state in which the brake pedal is depressed when a detection valueof brake sensor 126 is greater than or equal to a predetermined value.

The brake sensor is of a configuration capable of detecting a depressionamount of the brake pedal. However, a brake switch which detects adepression of the brake pedal as ON/OFF may also be adapted thereto, sothat a depression of the brake pedal is determined when the brake switchis turned ON.

Moreover, in addition to the above idle stop condition, there may be setan idle stop condition by adding or combining conditions such as: it isin a warm-up completion state in which the engine cooling watertemperature is greater than or equal to a predetermined value; the idleswitch 116 a is ON and the engine is determined to be in an idleoperating state, or the engine rotation speed Ne is within a setrotation speed range in an idle state; and the state of charge of thebattery is greater than or equal to a predetermined value which enablesrestarting.

After having performed the above automatic stop of the internalcombustion engine, when there has been detected a restart request causedby a brake release or a depression of the accelerator pedal performed bythe driver, that is to say, when the detection value of the brake sensoris less than or equal to the predetermined value, or when the brakeswitch OFF is detected or accelerator opening sensor APS 116 detects anaccelerator opening greater than or equal to a predetermined value,which is outside the idle operation range, the fuel injection amount ofeach cylinder is set as follows.

First, at the time of automatic stop, the inlet stroke stopped cylinderis determined and stored, and the fuel injection amount at the time ofrestarting (hereunder, referred to as restart time injection amount) issplit to perform injection a plurality of number of times. Here, thesplit injections in which the restart time injection amount is splitinto a plurality of number of times may be performed during a periodfrom the opening timing of the inlet valve to the closing timing of theinlet valve.

Moreover, when the inlet valve closing timing is controlled by anoperation of variable valve timing mechanism 201 and variable valve liftmechanism 112, to be after bottom dead center of the piston, and theengine is stopped, after the piston bottom dead center, even if theinlet valve is open when starting, the piston still rises after enginerotation. Therefore injected fuel is not easily sucked, and it becomesdifficult to introduce the restart time injection amount into thecylinder.

Consequently, it is preferable that split injections are completedbefore bottom dead center of the piston which is on the advanced side ofthe inlet valve closing timing.

By completing split injections at the piston bottom dead center orbefore bottom dead center, the split injections are completed in a statein which the piston is descending, that is to say, in a state in whichthe speed of suction into the cylinder by the piston is comparativelyhigh. Therefore, introduction of injected fuel into the cylinder becomeseasier, and superior combustion can be performed, thereby improvingstartability.

It is more preferable that the split injections are completed beforeapproaching the vicinity of 30° before bottom dead center. That is tosay, a delay occurs after injecting fuel from the fuel injection valveuntil it is introduced into the cylinder. Therefore taking this delayinto consideration, it is preferable that the timing at which the fuelinjected from the fuel injection valve is introduced into the cylinder,is set as a limit timing of the split injection completion timing, andthe split injections are completed before the limit timing is reached.

If in the vicinity of 30° before bottom dead center, the restart timeinjection amount can be introduced into the cylinder by performing splitinjections.

Moreover, when the inlet valve closing timing is controlled by anoperation of variable valve timing mechanism 201 and variable valve liftmechanism 112 to be at or before bottom dead center of the piston, it ispreferable that the split injections are completed before the closingtiming.

Furthermore, in this case also, so that the injected fuel is introducedinto the cylinder before the closing timing, it is preferable that thesplit injections are completed before the limit timing, which is setbefore the closing timing, taking into consideration the delay frominjection from the fuel injection valve until introduction into thecylinder. As a result, introduction of the injected fuel into thecylinder becomes easier, and superior combustion can be performed,thereby improving startability.

FIG. 2A shows a time chart of a first embodiment (the horizontal axis trepresents time).

In this embodiment, there is illustrated a case of performing splitinjection twice before engine rotation. Regarding the injection timing,injection timing of the initial injection is set immediately after arestart request has been detected, and injection timing of the secondinjection is set after a predetermined delay time Dspl has elapsed aftercompletion of the initial injection.

The second injection timing is set so as to satisfy the followingrelationship so that the second injection is completed before enginerotation is commenced.

Dspl<tw−tp1−tp2=tw−tp  (1)

where, tw represents a set time from a moment when a restart request ismade to a moment when the starter is activated and restarting (cranking)is commenced, tp1 represents the initial injection amount (injectiontime), and tp2 represents the second injection amount (injection time).Consequently, the starting time injection amount tp=tp1+tp2.

When tp1 equals tp2, then tp1=tp2=tp/2

As a result, in a cylinder which is in an inlet stroke immediately aftera restart request has been made, superior combustion can be commenced asdescribed below.

In the initial cycle after restarting, by splitting the starting timeinjection amount into a plurality of number of times including theinjection before engine rotation, split injections are performed insingle short injection times, and the resistance of air having no flowin the stop state becomes greater. Consequently, the penetration forceof the fuel spray injected from the fuel injection valve becomes weakand the amount of fuel becoming attached to the inlet air passage wallsurface is reduced, while the amount of fuel spay drifting inside theinlet air passage increases.

Here, regarding the inlet stroke stopped cylinder, since the inlet valveis open, the heat of high-temperature gas such as residual gas withinthe cylinder is transmitted to the inlet air passage side, and the airinside the inlet air passage is consequently excessively heated to ahigher temperature compared to that of the inlet air passage wall.Therefore, the increased amount of fuel spray drifting inside the inletair passage is exposed to the high-temperature air within the inlet airpassage and becomes evaporated, thereby increasing the air coolingeffect due to latent heat of vaporization. As a result, cooled inlet airis introduced into the cylinder when engine rotation is commenced.Therefore it is possible to suppress an increase in in-cylindertemperature in the compression stroke, and suppress the occurrence ofpre-ignition.

Incidentally, comparing with the conventional technique disclosed inPatent Document 1 above, in the conventional technique, the whole amountof a start request fuel injection amount is injected all at once beforethe engine rotates. Therefore the penetration force of the spray issignificant, and since there is no flow of the sucked air toward theinterior of the cylinder, the amount of fuel spray drifting within theinlet air passage decreases, and on the other hand, the amount of thefuel which becomes attached to the inlet air passage wall surfaceincreases. Therefore it is clear that the air cooling effect is low andthe occurrence of pre-ignition cannot be easily suppressed.

The initial injection timing before engine rotation is preferablyimmediately after a start request has been made. In this way, it ispossible to make the time to ignition timing or engine rotation longer,and thereby create a sufficient amount of evaporation time, thusenabling promotion of in-cylinder cooling.

On the other hand, the second injection timing is shown in the diagramas being when injection is completed immediately before engine rotationis commenced. However it is not limited to this timing. For example,preferably the second injection timing is set through experiment,simulation, or the like, to a timing where the cooling effect becomesgreatest. The same applies to the ratio between the first injectionamount and the second injection amount (split ratio).

Moreover, the configuration may be such that injections split into threetimes or more are performed before engine rotation. In this case, thesingle injection amount is reduced and the penetration force is furtherweakened. Therefore evaporation is facilitated and the effect ofsuppressing adhesion to the inlet port wall is also increased, so thatthe cooling effect of the air within the inlet port can be increased.

Next, there is described an embodiment in which, when restarting, aninjection is performed before engine rotation, for the initial cycle ofthe inlet stroke stopped cylinder, as well as after commencing enginerotation.

In a second embodiment shown in FIG. 2B, an injection amount which isset by splitting injection into two (½ of the restart time injectionamount) is injected respectively before engine rotation and after enginerotation. Regarding the injection timing, the injection commencingtiming when the engine is stopped is set to an injection commencingtiming of the initial injection immediately after the restart requesthas been detected. After completion of the injection when the engine isstopped, an injection commencing timing for injection after enginerotation is set after a predetermined delay time Dspl has elapsed, tocommence the second injection.

Using the respective values in the expression (1), this is set so as tosatisfy the following condition:

Dspl>tw−tp1  (2)

Next, there is described an operation and effect of the secondembodiment.

1) Regarding the inlet stroke stopped cylinder, since the inlet valve isopen, the heat of high-temperature gas such as residual gas within thecylinder is transmitted to the interior of the inlet air passage, andthe air inside the inlet air passage is consequently excessively heatedto a higher temperature compared to that of the inlet air passage wall.

Consequently, the restart time injection amount is split and set for thecylinder which is in an inlet stroke immediately after the restartrequest has been made. The first split injection is executed in a statebefore the engine rotates, where there is no air flow and the airresistance is high. Consequently, the penetration force of the fuelspray injected from the fuel injection valve becomes weak and the amountof fuel becoming attached to the inlet air passage wall surface isreduced, while the amount of fuel spay drifting inside the inlet airpassage increases. The increased fuel spray formed by the injectionbefore engine rotation and having a weak penetration force is exposed tohigh-temperature air within the inlet air passage and evaporates, andconsequently, the air cooling effect due to the latent heat ofvaporization is increased. Then this cooled inlet air is introduced intothe cylinder when engine rotation is commenced. Therefore it is possibleto suppress an increase in the in-cylinder temperature in thecompression stroke and suppress the occurrence of pre-ignition.

2) The fuel spray injected after engine rotation travels on the inletair flow and is introduced into the cylinder, and the air-fuel mixtureis dispersed and introduced into the cylinder while being diffused. Theair-fuel mixture within the cylinder (concentration) becomes uniform,and the effect of suppressing pre-ignition occurrence is furtherincreased.

FIG. 3A shows a third embodiment in which the number of splittings isset to three or more.

First, at the time of automatic stop, based on the piston position ofthe inlet stroke stopped cylinder, there is predicted a time tc from themoment when restart (cranking) of this cylinder is commenced to themoment when the inlet valve is closed. This prediction may be performedby experiment, simulation, or the like, and it may be set to a map orthe like as a predicted time tc corresponding to each piston position(or a total time is with tw described later). Moreover, since thecranking speed varies according to parameters such as battery voltage,state of charge, and cooling water temperature, the predicted time tcmay be corrected based on detection values of these parameters.

In an internal combustion engine in which the inlet valve closing timingis changed by an operation of variable valve timing mechanism 201 andvariable valve lift mechanism 112 according to the engine operatingstate when it is in an idle stop state, the inlet valve closing timingat the time of restarting is found based on the operating status ofvariable valve timing mechanism 201 and variable valve lift mechanism112, to thereby calculate the predicted time tc.

Moreover, as described above, when the inlet valve closing timing iscontrolled to be after bottom dead center of the piston by an operationof variable valve timing mechanism 201 and variable valve lift mechanism112, the split injections are to be completed before inlet bottom deadcenter, or more preferably before approaching the vicinity of 30° beforebottom dead center. Therefore, with consideration of a delay, whichoccurs after injecting fuel from the fuel injection valve until it isintroduced into the cylinder, it is preferable that the timing at whichthe fuel injected from the fuel injection valve is introduced into thecylinder is set as a limit timing of the split injection completiontiming, and the split injections are completed at or before the limittiming is reached. Therefore, in this case, the predicted time tc may bepredicted as a time tc from the moment after commencing restarting(cranking) to the moment when the limit timing is reached.

Moreover, the split injections are completed within the time from themoment when the restart request is detected to the moment when the inletvalve is closed, or within the time in which the limit timing isreached. That is to say, the split injections are completed during thetotal time is in which the predicted time tc until the inlet valve isclosed after commencing the restarting (cranking) or until the limittiming is reached, is added to the set time tw from the moment when therestart request was made to the moment when the starter is activated andrestarting (cranking) is commenced.

That is to say, the restart time injection amount tp is divided by thenumber of splits n to thereby set a single split injection amount, and adelay time Dspl which serves as a split injection interval time may beset so that the split injections are completed within the total time ts.

First, the number of splits n may be set to a preliminarily decidedvalue (3 to 5 for example), however, it may also be variably set basedon the above total time ts. For example, if the split number n is madehigh (low), then a single split injection amount becomes low (high), andthe amount of evaporation time required for this single injection amountdecreases (increases), however, the delay time Dspl also decreases(increases). Therefore, it is preferable that the delay time Dspl ismade greater than the required evaporation time, and the split number nis set to a number where the evaporation efficiency of the entirerestart time injection amount becomes highest.

Moreover, the injection commencing timing of the initial injection isset immediately after the restart request has been detected and a fuelinjection is executed. Having completed the injection, split injectionsare executed for the decided split number of times when each delay timeDspl has elapsed.

Next, there is described an operation and effect of the thirdembodiment.

The third embodiment exhibits at least one of the following effects.

1) When performing split injections three times or more, if the numberof injections before the engine rotates increases, the single injectionamount is further reduced and the penetration force thereof is furtherweakened. Therefore evaporation is further facilitated. As a result, theeffect of suppressing adhesion to the inlet port is also increased andthe amount of fuel spray drifting within the inlet air passageincreases. Therefore the cooling effect of the air within the inlet portdue to the latent heat of vaporization, can be increased.

2) If the number of injections after engine rotation is increased,injection can be continued intermittently in the inlet stroke.Therefore, disproportion in the injection amount in the inlet stroke canbe further reduced, and the uniformity of the air-fuel mixture withinthe cylinder can be further improved.

3) By reducing the injection amount in the vicinity of inlet strokecompletion, an injection amount according to the reduced gas flow isachieved. Furthermore, the uniformity of the air-fuel mixture within thecylinder can be improved.

Also in the third embodiment, there can be achieved the operation andeffects of increasing the effect of suppressing pre-ignition occurrenceby: 1) the cooling effect of the air within the inlet port due to theinjection before engine rotation having a weak penetration force; and 2)the uniformity of the air-fuel mixture in the cylinder achieved by theinjection after engine rotation, which are the operation and effectsdisclosed in the second embodiment above.

FIG. 3B shows a fourth embodiment. In this embodiment, in aconfiguration in which a single injection before and after enginerotation, that is, a total of two injections are performed, the firstinjection amount before engine rotation is higher than the secondinjection amount after engine rotation.

Regarding the injection timing, the injection commencing timing when theengine is stopped is set to an injection commencing timing of theinitial injection immediately after a restart request has been detected,to thereby perform an injection when the engine is stopped. After havingcompleted the injection, an injection commencing timing for an injectionafter engine rotation is set after a predetermined delay time Dspl haselapsed, to commence the second injection.

Using the respective values in the expression (1), this is set so as tosatisfy the following condition:

Dspl>tw−tp1  (2)

It is preferable that the amount of the initial fuel injection is set ina range in which evaporation is possible within the delay time Dspl. Asa result, the fuel injection after having commenced engine rotation canbe executed in a state in which the fuel of the initial injection hasevaporated. That is to say, if the fuel spray of the initial fuelinjection in a non-evaporated state impinges on the fuel spray injectedafter commencing engine rotation, the particle diameter thereofincreases and consequently vaporization becomes more unlikely, so thatpromotion of vaporization by the latent heat of vaporization is reduced.On the other hand, by setting the delay time Dspl so that the fuel ofthe initial injection evaporates, such a reduction in promotion ofvaporization can be suppressed.

Moreover, there may be provided a detection means which detects thetemperature within the inlet air passage (inlet air temperature), andthe initial fuel injection amount may be variably set according to thedetected temperature in the inlet air passage.

In this case, the amount of fuel which can evaporate within the delaytime Dspl can be made higher as the temperature within the inlet airpassage becomes higher. Therefore the initial fuel injection amount isset to an even higher amount.

As a result, since a higher amount of fuel can be set to the initialfuel injection amount when the inlet air temperature is comparativelyhigh, the effect of cooling due to the latent heat of vaporization canbe increased, and the inlet air temperature within the inlet air passagecan be reduced.

Detection of the temperature within the inlet air passage may beperformed with a configuration provided with a temperature sensor withinthe inlet air passage, or the temperature of the cylinder interior maybe detected directly or indirectly (estimated based on the cooling watertemperature or the like), and the temperature within the inlet airpassage then estimated based on the temperature of the cylinderinterior.

Next, there is described an operation and effect of the fourthembodiment.

In this embodiment, the first injection amount before engine rotationwhere the vaporization time until introduction into the cylinder can bemade long, is made greater than the second injection amount after enginerotation where the vaporization time is short, and thereby vaporizationefficiency can be improved.

Also in this embodiment, there can be achieved the operation and effectsof increasing the effect of suppressing pre-ignition occurrence by: 1)the cooling effect of the air within the inlet port due to the injectionbefore engine rotation having a weak penetration force; and 2) theuniformity of the air-fuel mixture in the cylinder achieved by theinjection after engine rotation, which are the operation and effectsdisclosed in the second embodiment above.

FIG. 4A shows a fifth embodiment. In this embodiment, in a configurationin which injections are split into three injections to be performed, theinjection amount is made greater when the injection is performedearlier, and the injection amount is made less when the injection ismade later.

When automatic stop is performed, as with the third embodiment, thesplit injection completion timing is controlled based on the pistonposition of the inlet stroke stopped cylinder. That is to say, a time tcfrom the moment after restarting (cranking) of the cylinder iscommenced, to the moment when the inlet valve is closed, or a time tcuntil the limit timing, which was used in the third embodiment, isreached, is predicted. The split injections are completed during thetotal time ts in which the predicted time tc is added to a time untilthe inlet valve is closed after detecting a restart request or until thelimit timing is reached, that is, a set time tw from the moment when therestart request was made to the moment when the starter is activated andrestarting (cranking) is commenced.

On the other hand, in this embodiment, an assigned ratio (%) of theindividual split injection amounts is preliminarily set where thestarting time injection amount is taken as 100%, and the starting timeinjection amount is multiplied by the assigned ratio to thereby setindividual injection amounts. A greater assigned ratio is set higherwhen the order of injection is earlier, and the assigned ratio is set sothat a higher injection amount is injected.

The number of splits n may be set to a preliminarily decided value (3 to5 for example), however, it may also be variably set based on the abovetotal time ts.

The delay time Dspl, which serves as a split injection interval time,may be set based on the restart time injection amount tp, the total timets, and the split number n, so that the split injections are completedwithin the total time ts.

Moreover, the injection commencing timing of the initial injection isset immediately after the restart request has been detected, and a fuelinjection is executed. Having completed the injection, split injectionsare executed the decided split number of times when each delay time Dsplhas elapsed.

Furthermore the delay time Dspl may be simply set as a single value,with which the intervals of the respective split injections are equal.However, as another setting method, by having the delay time Dspl madelonger for an earlier injection order, a longer vaporization time can beensured and it is possible to suppress impingement on the fuel spraycaused by the next split injection.

As a result, impingement of the fuel sprays between individual splitinjections can be suppressed, so that the reduction in the vaporizationefficiency caused by the increase in particle diameter of the fuel spraydue to impingement can be suppressed.

Next, there is described an operation and effect of the fifthembodiment.

In this embodiment, the injection amount is made greater for an earlierinjection which allows prolonged vaporization time until introductioninto the cylinder, and the injection amount is made less for a laterinjection in which vaporization time is short. Thereby vaporizationefficiency can be improved.

Also in the fifth embodiment, there can be achieved the operation andeffects of increasing the effect of suppressing pre-ignition occurrenceby: 1) the cooling effect of the air within the inlet port due to theinjection before engine rotation having a weak penetration force; and 2)the uniformity of the air-fuel mixture in the cylinder achieved by theinjection after engine rotation, which are the operation and effectsdisclosed in the second embodiment above.

FIG. 4B shows a sixth embodiment. In this embodiment, an engine rotationspeed (cranking speed) is detected after engine rotation has commenced,and when the rotation speed has reached a predetermined value, injectionafter engine rotation is commenced.

In this embodiment, an injection amount which is set by splitting theinjection into two (½ of the restart time injection amount) is injectedrespectively before engine rotation and after engine rotation. Regardingthe injection timing, the injection commencing timing when the engine isstopped is set to an injection commencing timing of the initialinjection immediately after the restart request has been detected, andafter completion of the injection when the engine is stopped, a splitinjection after engine rotation is executed when the engine rotationspeed Ne is determined to be greater than or equal to a predeterminedvalue.

This predetermined value is set for detecting engine rotation beingactually commenced by commencement of cranking for example, and it isset to a value less than or equal to the rotation speed of the idleoperation. The engine rotation speed may be calculated, for example,based on the angle at pulse occurrence of crank angle sensor 117 (forexample, 10°) and pulse interval time when the pulse occurs.

The number of split injections before engine rotation may be a pluralityof number of times. The number of split injections after engine rotationmay also be a plurality of number of times. The delay time Dspl ofinjection intervals may be set so that the injection completion timingof the final injection becomes less than or equal to the limit crankangle θerst where effective injection can be performed after enginerotation.

Moreover, the injection amount of an earlier split injection may be madegreater than that of a later split injection.

Next, there is described an operation and effect of the sixthembodiment.

In this embodiment, an actual engine rotation speed is detected, andinjection is commenced when the engine rotation speed has increased andthe flow velocity of inlet air into the cylinder has become high.Thereby, there is achieved an effect of promoting vaporization of thefuel spray and uniformity thereof inside the cylinder.

Incidentally, the injection completion timing of the injection afterengine rotation (the final injection when performing split injectionsthree times or more) needs to be completed before the inlet stroke iscompleted. Also in this case, as with the case of detecting a cylinderwhich is in an inlet stroke when automatic stop is performed, forexample, even if, as described later, the inlet valve closing timing isset after the piston bottom dead center, by a variable valve actuationmechanism, it is preferable that the injection completion timing of thefinal injection after engine rotation, is set at or before the inletbottom dead center. However, if there is a state in which the air-fuelmixture can be sucked into the cylinder after the inlet bottom deadcenter, by means of supercharging or the like performed by asupercharger during cranking, a completion timing of this suction(timing at which the effect of air-fuel mixture suction becomesinsufficient) may be set as an injection completion timing in the finalinjection after engine rotation.

Hereunder, embodiments which include control of completing the aboveinjection completion timing in the final injection after enginerotation, by the time of completion of the inlet stroke are described,with reference to the flow charts of FIG. 5A to 5D.

FIG. 5A corresponds to the first embodiment shown in FIG. 2A in whichsplit injections are performed only before engine rotation.

In step S1, it is determined whether the predetermined idle stopcondition described above is satisfied. If satisfied, control proceedsto step S2 in which fuel injection is stopped in order to automaticallystop the internal combustion engine.

In step S3, there is executed a process of stabilizing the engine stopposition. Specifically, the engine load (rotational resistance) isincreased, for example, by fully opening the throttle opening, andthereby the piston position of each cylinder when the engine is stoppedis stopped within a predetermined crank angle range, thereby suppressingvariation in the stop position. As a result, more stable startabilitycan be ensured. In addition to the procedure described above, anincrease in the engine load can also be made by controlling; the liftamount and operating angle of the inlet valve, the valve timing, and thepower generation of the alternator, and on a hybrid vehicle, bycontrolling the drive electric motor.

After engine rotation is stopped in the process of step S3, in step S4 acylinder which is in an inlet stroke in a stop state is determined basedon a signal from crank angle sensor 117, and also the piston position(crank angle position) of the inlet stroke stopped cylinder is detected,and stored in a backup memory.

In step S5, it is determined whether the stored crank angle θ of theinlet stroke stopped cylinder (the angle from the inlet top dead center)is less than or equal to a limit crank angle θerst′ (advanced side).This limit crank angle θerst′ is set as a limit crank angle θ at whichthe fuel spray within the inlet air passage split-injected before enginerotation after the engine is automatically stopped by an idle-stopcontrol can be sufficiently sucked into the cylinder by the time of theinlet stroke completion after engine rotation. That is to say, even withthe inlet stroke stopped cylinder, if the inlet stroke which remainsafter engine rotation is too short, the spray injected into the inletair passage before engine rotation cannot be sufficiently sucked intothe cylinder, and consequently it is difficult to commence a superiorrestart in this cylinder. Therefore, in this case, in order to prohibitsplit injections before engine rotation, the above determination isperformed.

In step S5, if the crank angle θ of the inlet stroke stopped cylinder isdetermined to be less than or equal to the limit crank angle θerst′, itis judged that the spray within the inlet air passage made by the splitinjection before engine rotation is sufficiently sucked after enginerotation.

Therefore, control proceeds to step S6 in which a restart time injectionamount tp is set based on a water temperature, and this restart timeinjection amount tp is divided by the split number n to therebycalculate the injection amount tpn of each injection. At the same time,a delay time Dspl which serves as the interval time between therespective split injections is calculated.

Next, in step S7, an occurrence of a restart request such as adepressing operation of the accelerator is determined.

If it is determined in step S7 that a restart request has occurred,control proceeds to step S8, and a fuel injection before engine rotation(first injection) is commenced.

Subsequently, in step S9, after the injection is completed in step S8, asecond split injection is performed after the delay time Dspl haselapsed. In a case in which split injection is performed three times ormore, a subsequently split injection is performed after the delay timeDspl has elapsed after each split injection is completed, to therebycomplete the split injection before engine rotation.

In step S10, after the restart request has occurred, the starter isactivated after a predetermined delay time tw has elapsed, and enginestart (cranking) is commenced.

On the other hand, if the crank angle θ of the inlet stroke stoppedcylinder is determined to be greater than the limit crank angle θerst′(retarded side) in step S5, it is judged that split injection cannot beperformed in this cylinder.

In this case, control proceeds to step S11 in which a restart timeinjection amount is set, and after having determined the restart requestbeing satisfied in step S12, in step S13, the set restart time injectionamount of fuel is injected at once into the cylinder which has beenstopped in an exhaust stroke.

FIG. 5B shows a flow of the embodiment in which a single split injectionis respectively performed before and after engine rotation.

Step S1 to step S4 are similar to those in FIG. 5A in that when apredetermined idle stop condition is satisfied, fuel injection isstopped in order to automatically stop the internal combustion engine,and after having executed a process of stabilizing the engine stopposition, the inlet stroke stopped cylinder is determined, and thepiston position thereof (crank angle position) is detected and stored.

In step S21, it is determined whether the stored crank angle θ of theinlet stroke stopped cylinder is less than or equal to the limit crankangle θerst at which a split injection, in particular, an effectiveinjection after engine rotation can be performed when restarting.

If it is determined in step S21 that the crank angle θ of the inletstroke stopped cylinder is less than or equal to the limit crank angleθerst, control proceeds to step S22.

In step S22, a fuel injection amount at the time of restarting(hereunder, referred to as restart time injection amount) is set basedon water temperature, and also use of the split injection method isdetermined, and the restart time injection amount tp is divided by thesplit number (twice) to thereby calculate the split injection amount tpnof each injection.

As described above, in the second embodiment shown in FIG. 2B, theamount of two split injections tpn is set equal (tp1=tp2=tp/2), and inthe fourth embodiment shown in FIG. 3B, the first injection amount tp1(before engine rotation) is set to an amount greater than the secondsplit injection amount tp2 (after engine rotation).

For example, in a case in which the injection commencing timing of thesecond split injection is set immediately after commencement ofrestarting (cranking), then in accordance with this setting, a delaytime Dspl, which serves as an injection interval time from thecompletion of the first injection to the commencement of the secondinjection, is initially set as shown in the following expression.

Dspl=tw−tp1  (3)

Next, in step S23, in the above split injections, an injectioncompletion timing θend of the second injection after engine rotation,which has been found based on the split injection amounts tp1 and tp2 ofthe respective injections and the initial injection interval value(delay time Dspl), is compared with a limit crank angle (air-fuelmixture suction limit crank angle) θitend at which the effect ofair-fuel mixture suction can be maintained at an excellent level.

The air-fuel mixture suction limit crank angle may normally be the inletbottom dead center as described above. However, this may be at the inletvalve closing timing when the inlet valve closing timing is after theinlet bottom dead center in a case of performing supercharging with useof a supercharger.

Moreover, the limit crank angle (limit timing) θitend may be set basedon the operating state of variable valve timing mechanism 201 andvariable valve lift mechanism 112 when the engine is in a stop state,that is to say, it may be set based on the closing timing of the inletvalve.

Furthermore, the air-fuel mixture suction limit crank angle θitend setbased on these may be set as a crank angle on the advanced side to theinlet bottom dead center or the inlet valve closing timing describedabove, with consideration of the delay from the moment of fuel injectionto the moment of introduction into the cylinder.

If θend>θitend is determined in step S23, the delay time Dspl of splitinjection is reduction-corrected in step S24 so that θend≦θitend issatisfied. Subsequently, control proceeds to step S25 in which it isdetermined whether an engine restart request has occurred in a state inwhich the engine is automatically stopped.

By setting the fuel injection amount at the time of restarting in theautomatic stop state in this manner, calculation delay can besuppressed, fuel injection delay in response to the restart request canbe reduced, and the starting time can be reduced, thereby improvingstartability, compared to the case of calculating a fuel injectionamount after a restart request has been detected.

If it is determined in step S25 that a restart request has occurred,control proceeds to step S26, and a fuel injection before enginerotation stop (first injection) is commenced.

In step S26, after the restart request has occurred, the starter isactivated after a predetermined delay time tw has elapsed, and enginestart (cranking) is commenced.

In step S27, after completion of the first injection before enginerotation, the second fuel injection after engine rotation is performedafter the delay time Dspl has elapsed, and then this routine ends.

Here, if step S23 determines at the beginning that θend≦θitend issatisfied and the delay time Dspl is an initially set value, a fuelinjection after engine rotation is commenced, after engine rotation(cranking) has been commenced by starter activation.

On the other hand, in a case in which it is determined in the beginningthat θend>θitend is satisfied as shown in FIG. 6A and the delay timeDspl has been reduction-corrected, the second injection commencingtiming is brought to a earlier timing as shown in FIG. 6B. Therefore, ifthe amount of reduction correction is high, fuel injection is commencedbefore engine rotation, and the injection may end after engine rotationin some cases.

By making the injection intervals smaller in this way, split injectionsare executed in the inlet stroke stopped cylinder to the greatestpossible extent and prompt combustion is commenced, and thereby thestart completion time can be reduced and startability can be improved.

Moreover, if the crank angle θ of the inlet stroke stopped cylinder isdetermined to be greater than the limit crank angle θerst in step S21 asshown in FIG. 7A, it is judged that split injection cannot be performedin this cylinder. Then, control proceeds to step S11 in which a restarttime injection amount is set, and after having determined the restartrequest being satisfied in step S12, in step S13, the set restart timeinjection amount of fuel is injected into the cylinder which has beenstopped in an exhaust stroke as shown in FIG. 7B.

If a fuel injection is also performed in a case in which, even if fuelhas been injected into the inlet stroke stopped cylinder, suction of theinjected fuel can be hardly done in the inlet stroke, and consequentlycombustion is not performed, then in the subsequent inlet stroke, ahighly concentrated air-fuel mixture is sucked along with the fuelre-injected in the immediately prior exhaust stroke, and consequently amisfire may occur, or the rotation speed may drop due to insufficientoutput power in some cases.

In a case in which injected fuel can be hardly sucked in the inletstroke as with the present embodiment, by stopping (prohibiting) fuelinjection into the cylinder, the above misfire and drop in rotationspeed can be suppressed, and startability can be stabilized.

FIG. 5C shows a flow of the embodiment in which a split injection isrespectively performed before and after engine rotation, and the splitnumber n is three times or more.

Step S1 to step S4, and step S21 are similar to those in FIG. 5B in thatwhen a predetermined idle stop condition is satisfied, fuel injection isstopped in order to automatically stop the internal combustion engine.Then, after having executed a process of stabilizing the engine stopposition, the inlet stroke stopped cylinder is determined, and thepiston position (crank angle position) thereof is detected and stored.Then, it is determined whether the crank angle θ of the inlet strokestopped cylinder is less than or equal to the limit crank angle θerst atwhich an effective split injection can be performed after enginerotation at the time of restarting.

If it is determined in step S21 that the crank angle θ of the inletstroke stopped cylinder is less than or equal to the limit crank angleθerst, use of the split injection method is determined and controlproceeds to step S31. In step S31, a restart time injection amount tp isset based on water temperature, and a split number n, a split injectionamount tpn of each injection, and a delay time Dspl which serves as aninjection interval time are calculated based on the crank angle θ of theinlet stroke stopped cylinder.

Specifically, based on the piston position (crank angle position) of theinlet stroke stopped cylinder as described above, an amount of timerequired from the moment when the restart request is detected to themoment when the air-fuel mixture suction limit crank angle θitend isreached is predicted, and the above respective values are set so thatsplit injections can be completed within this predicted amount of time.

In the third embodiment shown in FIG. 3A, the split injection amount tpnof each injection is set equal (tpn=tp/n), and the delay time Dsplbetween the respective split injections is also set equal. On the otherhand, in the fifth embodiment shown in FIG. 4A, it is preferable thatthe split injection amount tpn is set higher for an earlier injection,and regarding the delay time Dspl, this is set higher for an injectioninterval at earlier timing.

Subsequently, control proceeds to step S32 in which it is determinedwhether an engine restart request has occurred in a state in which theengine automatically stopped.

If it is determined in step S32 that a restart request has occurred,control proceeds to step S33, and a fuel injection before enginerotation stop (first injection) is commenced.

In step S34, after completion of the first injection before enginerotation, the second fuel injection after engine rotation is performedafter the delay time Dspl has elapsed, and subsequently, there isrepeated control in which after completion of each injection, the nextsplit injection is commenced after the delay time Dspl has elapsed.

In step S35, after the restart request has occurred, the starter isactivated after a predetermined delay time tw has elapsed, and enginestart (cranking) is commenced.

In step S36, also after restarting, there is continued the control ofsplit injections at the above delay time Dspl intervals, until injectionends within the air-fuel mixture suction limit crank angle θitend.

Moreover, if it is determined in step S21 that the crank angle θ of theinlet stroke stopped cylinder is greater than the limit crank angleθerst, as with the case of FIG. 5B, it is judged that split injectioncannot be performed in this cylinder. Then, a restart time injectionamount is set in step S11, and after having determined the restartrequest being satisfied in step S12, in step S13, the set restart timeinjection amount of fuel is injected into the cylinder which has beenstopped in the exhaust stroke.

Furthermore, FIG. 5C may be applicable to a configuration in which atotal of two split injections are performed, that is to say, a singlesplit injection is performed respectively before and after enginerotation.

FIG. 5D shows a flow of the embodiment (the fifth embodiment shown inFIG. 4A) in which the timing of commencing the second split injectionafter engine rotation is set at the moment when the engine rotationspeed reaches a predetermined value.

Step S1 to step S4 are similar to those in FIG. 5A to FIG. 5C in thatwhen a predetermined idle stop condition is satisfied, fuel injection isstopped in order to automatically stop the internal combustion engine,and after having executed a process of stabilizing the engine stopposition, the inlet stroke stopped cylinder is determined and the pistonposition thereof (crank angle position) is detected and stored.

In step S41, in a case in which the crank angle θ of the inlet strokestopped cylinder is such that the second split injection is commencedwhen the engine rotation speed Ne has reached a predetermined value Ne0after restarting, it is determined whether this split injection can becompleted within the air-fuel mixture suction limit crank angle θitend.

If it is determined that the injection can be completed within theair-fuel mixture suction limit crank angle θitend, control proceeds tostep S42 to perform split injections.

In step S42, a restart time injection amount and a split injectionamount are set.

If it is determined in step S43 that a restart request has occurred,control proceeds to step S44, and a fuel injection before enginerotation stop (first injection) is commenced.

In step S45, after the restart request has occurred, the starter isactivated after a predetermined delay time tw has elapsed, and enginestart (cranking) is commenced.

In step S46, it is determined whether the engine rotation speed Ne hasreached the predetermined value Ne0 or a greater value after the enginehas been restarted. The predetermined value Ne0 is set to a value atwhich the inlet air flow velocity in the cylinder has increased due tothe increase in the engine rotation speed Ne, and the effect ofin-cylinder diffusion of the injected spray is high.

In step S46, if it is determined that the engine rotation speed Ne hasreached the predetermined value Ne0 or a greater value, control proceedsto step S47 and the second split injection is commenced.

On the other hand, in step S41, in a case in which the second splitinjection is commenced at an engine rotation speed Ne greater than orequal to the predetermined value Ne0, if it is determined that thisinjection may not be completed within the air-fuel mixture suction limitcrank angle θitend, a restart time injection amount is set in step S11,and after having determined the restart request being satisfied in stepS12, in step S13, the set restart time injection amount of fuel isinjected into the cylinder which has been stopped in the exhaust stroke.

Moreover, control may proceed to step S21 and the subsequent steps ofFIG. 5B if the second split injection has been commenced at an enginerotation speed Ne greater than or equal to the predetermined value Ne0in step S41. In this case, if the crank angle θ of the inlet strokestopped cylinder is less than or equal to the limit crank angle θerst,split injections can be executed.

FIG. 5E shows a flow of a seventh embodiment in which a restart requestafter a warm-up completion is judged, and fuel injection control at thetime of restarting is executed as described in the respectiveembodiments of FIG. 5A to FIG. 5D.

In step S51, it is determined whether a start commencing operation hasbeen performed by an engine start switch (such as an ignition switch ora push-type start button).

If no start commencing operation has been performed, control proceeds tostep S57 in which it is determined whether the engine is stopped by anOFF operation of the engine start switch. If YES, control proceeds tostep S58 in which the cylinder in the inlet stroke is determined basedon a signal from the crank angle sensor 117 in an engine stop state, andthe piston position of the inlet stroke stopped cylinder (crank angleposition) is detected and stored into the backup memory. If thedetermination result of step S57 is NO, this flow ends.

On the other hand, if it is determined in step S51 that a startcommencing operation has been performed by the engine start switch,control proceeds to step S52 and detection values of engine temperature(engine cooling water temperature, lubricating oil temperature, and thelike) are read.

In step S53, it is determined whether the engine temperature is belowthe warm-up completion temperature.

If it is determined as being a low-temperature start at an enginetemperature below the warm-up completion temperature, control proceedsto step S54 in which the starter is activated to commence cranking, anda cylinder determination is performed based on a signal from the crankangle sensor 117. This cylinder determination is performed in a mannersuch that the result stored in step S58 is cleared and a determinationis made again.

Since the vaporizability of fuel becomes lower and the amount of fuelwhich becomes attached to the inlet air passage wall increases when theengine temperature is lower, in step S55, the fuel injection amount isincrease-corrected and fuel injection is executed in the exhaust stroke(normal low-temperature injection amount control).

On the other hand, if it is determined in step S54 that the enginetemperature is greater than or equal to the warm-up completiontemperature, a warm-up start is performed under a condition similar tothat at the time of restarting after an idle stop, and therefore thereis performed control similar to any one of the respective embodimentsshown in FIG. 5A to FIG. 5D (step S5 and subsequent steps in FIG. 5A,step S21 and subsequent steps in FIGS. 5B and 5C, and step S41 andsubsequent steps in FIG. 5D).

According to the seventh embodiment, also at the time of performingwarm-up start with an engine start switch operation performed by thedriver, there is obtained the operation and effect of the correspondingembodiment among the first to sixth embodiments described above.

Moreover, although the seventh embodiment may be practiced incombination with the first to sixth embodiments at the time of a startrequest after automatic stop is performed, the seventh embodiment can ofcourse be independently practiced on a vehicle in which automatic stopsuch as idle stop is not performed.

In the embodiment described above, split injections can be easilyperformed a plurality of number of times before engine rotation, bysetting a split number n1 before engine rotation, each split injectionamount tpn1, and a delay time Dspl1 with respect to the injection amountbefore engine rotation. Split injections after engine rotation may alsobe performed a plurality of number of times, and a split number n2 afterengine rotation, each split injection amount tpn2, and a delay timeDspl2 are similarly set with respect to the injection amount afterengine rotation. Furthermore, when the engine rotation speed Ne hasreached the predetermined value Ne0 and injection has been commenced instep S41, it may be determined whether the final injection can becompleted within the air-fuel mixture suction limit crank angle θitend,and it may be executed if this injection completion is possible.

Furthermore, in the above embodiment, when a split injection isperformed in the initial cycle for the inlet stroke stopped cylinder, atthe same time, the restart time injection amount of fuel is injectedinto the cylinder stopped in the exhaust stroke immediately after arestart request has been made. Subsequently, injection is commenced forthe cylinder in the exhaust stroke at a predetermined injectioncommencing timing. However the control is switched after the secondcycle, or once engine rotation has been stabilized after a completeexplosion, so that the injection completion timing becomes constant.

Moreover, as has been described, an injection before engine rotationcontributes to cooling of air inside the inlet port while an injectionafter engine rotation contributes to uniformity of air-fuel mixtureinside the cylinder, and these injections respectively have an effect ofsuppressing pre-ignition. Consequently, with a long stroke engine or anengine having a tumble control valve added thereto and having acomparatively high gas flow and a high level of air-fuel mixtureuniformity in the cylinders, the entire injection amount may besplit-injected only before engine rotation as with the first embodiment.Moreover, with an engine in which the injection amount before enginerotation is made relatively high to enhance the cooling capability, andair-fuel mixture uniformity in the cylinders is low, the injectionamount after engine rotation may be made relatively high so as toenhance the uniformity.

Furthermore, in order to improve startability, there may also be used incombination a control in which the inlet valve closing timing iscontrolled to a most retarded position to reduce the compressionpressure, using variable valve timing mechanism 201 at the time of idlestop.

FIG. 8 shows a flow chart of valve closing timing control of the aboveinlet valve.

In step S101, it is determined whether an idle stop condition issatisfied. If satisfied, control proceeds to step S102 in which thevalve timing of the inlet valve is made most retarded by variable valvetiming mechanism (VTC) 201, thereby executing control to make inletvalve closing timing (IVC) retarded to the greatest possible extent.

Moreover, in a case of mechanically driving to be most retarded, bystopping power distribution to a control actuator of variable valvetiming mechanism 201, power distribution to the control actuator may bestopped to thereby shift the valve timing of the inlet valve to the mostretarded side.

Furthermore, it is preferable that variable valve lift mechanism 112executes control so that the lift amount and operating angle of theinlet valve are on the greater side (where the lift amount is maximumfor example).

Here, by using the most retard control of the valve timing performed byvariable valve timing mechanism 201 in combination with the inlet valveoperating angle control of variable valve lift mechanism 112, IVC can bemade further retarded, and it becomes possible to expand the range ofIVC control required for pre-ignition suppression.

In this case, the control actuator of variable valve lift mechanism 112is driven until at least the engine is stopped, and thereby the highlift amount side of the inlet valve is retained.

Moreover, power distribution may be performed even when the engine is inthe stop state, in order to continue to drive the control actuator ofvariable valve lift mechanism 112. Furthermore, power distribution maybe stopped when the engine has been stopped and it may be restored whenan automatic start request is made.

In step S103, it is determined whether the valve timing of the inletvalve has been shifted to the most retarded position by variable timingmechanism 201, and this control continues to be performed until it isdetermined as having been shifted.

Whether or not the valve timing of the inlet valve has been shifted tothe most retarded position can be determined when the actual advancedisplacement amount of variable valve timing mechanism 201 takes a valueshowing the most retarded position. This actual advance displacementamount can be calculated based on the rotational phase differencebetween the inlet cam shaft and the crank shaft.

After the engine has been stopped in step S104, a restart request occursdue to the determination in step S105, and the restart control describedabove is performed.

Then, in step S106, if the start completion is determined (for example,when the start switch is OFF and the engine rotation speed has reached avalue corresponding to a complete explosion), in step S107, the controlof bringing the valve timing of the inlet valve to the most retardedposition is released, and the control is switched to employ a targetvalve timing of the inlet valve, which is set based on the engineoperating state.

FIG. 9 shows a time chart of the above IVC control.

When the accelerator opening is reduced and the engine operation isbrought to a deceleration idle state in which idle switch 116 a isturned ON, the target value of the valve timing control of the inletvalve performed by variable valve timing mechanism (VTC) 201 is set to aretarded value according to the deceleration idle state, and the valvetiming is retard-controlled so as to approach this target value.

Moreover, the target values of the lift amount and of the operatingangle control of the inlet valve performed by variable valve liftmechanism (VEL) 112 are also set to values at which the operating angleis reduced according to the deceleration idle state, and areduction-control is performed so that the lift amount and the operatingangle approach these target values.

With these retardation control and reduction control of the lift amountand the operating angle of the inlet valve, the inlet valve openingtiming is retarded, and the amount of valve overlapping with the exhaustvalve is reduced. Consequently, combustion characteristics in thedeceleration idle state can be maintained at a superior level.

When the vehicle traveling speed is reduced by the deceleration idlestate, to a speed below an idle stop determination vehicle travelingspeed, and the idle stop condition is satisfied, the pre-ignitionavoidance control is commenced as described above. As a result, thetarget value of the valve timing control of the inlet valve performed byvariable valve timing mechanism (VTC) 201 is set to the most retardedposition, and control is performed so that valve timing approaches themost retarded position.

On the other hand, in a case in which as described above, thepre-ignition avoidance control with variable valve lift mechanism 112 isused in combination, the target value is set so that the lift amount andoperating angle of the inlet valve are on the greater side (where thelift amount is maximum for example), and increase-control is performedso that the lift amount and the operating angle approach the targetvalues.

The most retard control of the valve timing of the inlet valve performedby variable valve timing mechanism 201 continues to be performed untilthe most retarded position, which is the target value, is determined asbeing reached. Moreover, in a case in which the pre-ignition avoidancecontrol performed by variable valve lift mechanism 112 is used incombination, the control continues to be performed until it isdetermined that the lift amount and operating angle of the inlet valvehave reached the target values. However, power distribution may beperformed even when the engine is in a stop state in order to continueto drive the control actuator (state shown in the diagram), or powerdistribution may be stopped when the engine has been stopped and it maybe restored when an automatic start request is made.

After the engine is stopped as described above, when an increase in theaccelerator opening caused by a depressing operation of the acceleratorpedal is detected and a restart request occurrence is detected, thestart switch is turned ON and restarting (cranking) is commenced. As aresult, when the engine rotation speed reaches a predetermined value orhigher and causes the starter switch to turn OFF, and the enginerotation speed has reached a value corresponding to a complete explosionand start completion is determined, the most retard control of the valvetiming of the inlet valve performed by variable valve mechanism 201 isreleased. Moreover, in a case in which the increase-control of the valvetiming of the inlet valve performed by the variable valve lift mechanism112 is used in combination, this control is also released and thecontrol is switched to employ new target values, which are respectivelyset based on the engine operating state.

If there is performed the most retard control of the valve timing of theinlet valve performed by variable valve timing mechanism 201, or controlwhich combines the most retard control of the valve timing of the inletvalve performed by variable valve timing mechanism 201 with theincrease-control of the lift amount and operating angle of the inletvalve performed by variable valve lift mechanism 112, the inlet valveclosing timing (IVC) is in a most retarded position at the time ofrestarting after the idle stop has been released. As a resultcompression pressure is reduced and startability of the engine can befurther improved.

Furthermore, there is a fuel injection valve in which sprays injectedfrom a plurality of injection nozzles are made to impinge on each otherto thereby promote atomization of the fuel (refer to Japanese Patent No.4099075).

The relevant parts structure and operation of the above fuel sprayimpingement type fuel injection valve is described, with reference tothe drawings.

As shown in FIG. 10A to FIG. 100, a nozzle plate 18 provided so as tocover an injection nozzle 8C on a valve seat member 8 includes; a flatplate section 18A which is formed in a disk shape by applyingpress-working to a metallic plate for example, and a cylinder section18B which is formed bent in a substantially L shape toward the outerperiphery side of the flat plate section 18A.

Flat plate section 18A is joined with the tip end surface of valve seatmember 8 by a welding section 19, and cylinder section 18B is joinedwith the inner circumferential surface of a small diameter cylindersection 2B of a valve casing 2 by a welding section 20.

A plurality of nozzle holes 21 provided in flat plate section 18A ofnozzle plate 18 are provided in a total of 12 locations in the center offlat plate section 18A as shown in FIG. 100 and FIG. 10D for example,and fuel inside casing 1 is injected therefrom when a valve body 9 isopen.

Here, the respective nozzle holes 21 form six nozzle hole pairs 22, 23,24, 25, 26, and 27 respectively having a pair of two adjacent nozzleholes 21A and 21B, and nozzle hole pairs 22, 23, and 24 and nozzle holepairs 25, 26, and 27 are arranged line-symmetric about the X-X axiswhich passes through the center of nozzle plate 18. First nozzle holepairs 22 and 25 among these nozzle hole pairs 22, 23, 24, 25, 26, and 27are arranged along the X-X axis in the vicinity of the X-X axis as shownin FIG. 10D, and second nozzle hole pairs 23, 24, 26, and 27 arearranged in positions different in the circumferential direction ofnozzle plate 18 from those of first nozzle hole pairs 22 and 25 anddistanced from the X-X axis further than first nozzle hole pairs 22 and25 to the outer periphery side of nozzle plate 18.

Nozzle holes 21A and 21B which form the respective nozzle hole pairs 22to 27 are of a configuration such that as shown in FIG. 10E, the holecenters A-A and B-B thereof are respectively inclined only by an angle θwith respect to the Y-Y axis orthogonal to flat plate section 18A ofnozzle plate 18, and they intersect with each other in a V shape aboutthe Y-Y axis.

As a result, each of nozzle hole pairs 22 to 27 is configured as animpingement type nozzle hole pair in which injection flows of fuelinjected from the respective nozzle holes 21A and 21B in the directionshown with arrows F impinge on each other on the forward side in theinjection directions. The spray of fuel after the impingement caused byfirst nozzle hole pairs 22 and 25 forms spray patterns 28 and 31 shownin FIG. 10D. Moreover, the spray of fuel after the impingement caused bysecond nozzle hole pairs 23, 24, 26, and 27 form other spray patterns29, 30, 32, and 33, the spraying directions of which are different fromthose of spray patterns 28 and 31 formed by first nozzle hole pairs 22and 25.

Nozzle hole pairs 22 to 27 atomize the fuel by causing the injectionflows of fuel injected from nozzle holes 21A and 21B to impinge on eachother, and inject this fuel to the outside in spray patterns 28, 29, 30,31, 32, and 33 shown in FIG. 10D. At this time, spray patterns 28, 29,30, 31, 32, and 33 respectively have different spraying directions so asto be line-symmetric about the X-X axis as shown in FIG. 10D.

Here, in this embodiment, as shown in FIG. 10E, the dimensional ratiot/d between the plate thickness t of nozzle plate 18 (flat plate section18A) and the hole diameter d of nozzle holes 21A and 21B is set so as tosatisfy a relationship t/d≧1.0.

As a result, the length L of nozzle holes 21A and 21B provided in nozzleplate 18 can be made long, so that straight progression of the injectionflow can be ensured when injecting fuel in the arrow F direction fromeach of nozzle holes 21A and 21B.

Therefore, in the provided configuration, atomization of the fuel can bepromoted by making the injection flows injected from nozzle holes 21Aand 21B of the respective nozzle hole pairs 22 to 27 appropriatelyimpinge on each other, and spray patterns 28 to 33 from nozzle holepairs 22 to 27 can be expanded extensively.

With use of this spray impingement type fuel injection valve,impingement between sprays promotes fuel atomization and the spraypatterns expand extensively, and consequently the penetration forcebecomes reduced. Therefore, the atomized fuel spray, in particular, thefuel spray injected before engine rotation in the inlet stroke stoppedcylinder, efficiently cools the inlet port wall and the air-fuel mixturewithin the inlet port while spray adhesion to the inlet valve is beingsuppressed, and the cooling effect thereof within a cylinder when suckedinto the cylinder can be increased and the effect of suppressingpre-ignition can be increased.

Moreover, atomization of the fuel can be further promoted by increasingthe fuel pressure supplied to the fuel injection valve at the time ofrestarting.

FIG. 11 shows a flow of a relevant part of a fuel pressure raisingcontrol at the time of restarting. In step S9 in the flow chart of FIG.5A, when a restart request occurrence has been determined, controlproceeds to step S21 and fuel pressure raising control is executed. Forexample, it is possible to raise the fuel pressure to be supplied to thefuel injection valve by increasing pump rotation speed from that at thetime of idle operating by changing the battery, which supplies electricpower to an electric fuel pump (not shown in the drawing), from normallead battery 121 to lithium-ion battery 122.

Next, in step S22, it is determined whether the actual fuel pressuredetected by a fuel pressure sensor (not shown in the drawing) hasreached a target fuel pressure. After it has been reached, controlproceeds to step S10 and the first fuel injection before engine rotationis executed in the inlet stroke stopped cylinder. Other steps aresimilar to those in FIG. 5A.

Furthermore, when automatically stopping the internal combustion engine,if fuel pressure raising control is performed before the engine isstopped, to increase the fuel pressure within the fuel tubing, theamount of time required for the fuel pressure to reach the target fuelpressure is reduced when performing the fuel pressure raising control atthe time of restarting, and the commencement of the first injectionbefore engine rotation can be performed earlier, accordingly allowingprolonged vaporization time.

Although not shown in the drawing, fuel consumption may be improved bychanging the fuel pump power supply source to a lead battery to reducethe fuel pressure to the normal fuel pressure, after starting has beencompleted (complete explosion).

If this fuel pressure raising control at the time of restarting is usedin combination with the spray impingement type fuel injection valve,improved atomization increases the cooling effect within the cylinderand the effect of suppressing pre-ignition can be further increased.However, even if this is applied to a system which uses a normal fuelinjection valve (non-spray-impingement type), it is of course possibleto increase the effect of suppressing pre-ignition.

The entire contents of Japanese Patent Application No. 2009-282946 filedon Dec. 14, 2009 a priority of which is claimed, are incorporated hereinby reference.

While only selected embodiments have been chosen to illustrate anddescribe the present invention, it will be apparent to those skilled inthe art from this disclosure that various changes and modifications canbe made herein without departing from the scope of the invention asdefined in the appended claims.

Furthermore, the foregoing description of the embodiments according tothe present invention is provided for illustration only, and not for thepurpose of limiting the invention as defined by the appended claims andtheir equivalents.

1. An apparatus for controlling fuel injection of an internal combustionengine for a vehicle comprising: a fuel injection valve arranged so asto inject fuel to an inlet port of each cylinder of the internalcombustion engine; and a control unit which controls driving of the fuelinjection valve comprising: an inlet stroke stopped cylinderdetermination section which determines a cylinder stopped in an inletstroke when the internal combustion engine is stopped; a start requestdetection section which detects a start request of the internalcombustion engine; and a start-commencement cylinder injection controlsection which, when starting the engine upon detection of the startrequest, splits fuel injection of the initial cycle to the cylinder,which has been determined as being stopped in the inlet stroke when theinternal combustion engine was stopped before starting, into a pluralityof injections at least including an injection before engine rotation, tothereby perform injections.
 2. An apparatus according to claim 1,wherein the control unit further comprises: an automatic engine stopsection which stops fuel injection when the vehicle stops to therebyautomatically stop the operation of the internal combustion engine; andthe inlet stroke stopped cylinder determination section determines acylinder which has been stopped in an inlet stroke when the internalcombustion engine is automatically stopped; the start request detectionsection detects a start request of the internal combustion engine, whichhas been automatically stopped; and the start-commencement cylinderinjection control section, when starting the engine upon detection ofthe start request after the internal combustion engine has beenautomatically stopped, splits fuel injection of the initial cycle to thecylinder, which has been automatically stopped in the inlet stroke, intoa plurality of injections at least including an injection before enginerotation, to thereby perform injections.
 3. An apparatus according toclaim 1, further comprising: an engine temperature detector whichdetects an engine temperature; and the control unit further comprises: awarm-up completion state determination section which determines awarm-up completion state in which the detected engine temperature isgreater than or equal to a predetermined temperature; and thestart-commencement cylinder injection control section, when starting theengine upon the start request detection in the determined warm-upcompletion state, splits fuel injection of the initial cycle to thecylinder, which has been determined as being stopped in the inlet strokewhen the internal combustion engine was stopped before starting, into aplurality of injections at least including an injection before enginerotation, to thereby perform injections.
 4. An apparatus according toclaim 3, wherein the control unit is separately formed as: a fuelcontrol unit which controls driving of the fuel injection valve; and anautomatic stop control unit which outputs; an automatic stop requestwhich stops driving the fuel injection valve when the vehicle is stoppedto thereby automatically stop the operation of the internal combustionengine, and a start request of the internal combustion engine which hasbeen automatically stopped, to the fuel control unit, and the fuelcontrol unit comprises: a fuel injection valve drive stop section whichstops fuel injection based on a start request signal from the automaticstop control unit to thereby stop the operation of the internalcombustion engine; an inlet stroke cylinder determination section whichdetermines a cylinder stopped in an inlet stroke when the internalcombustion engine is automatically stopped; and a start-commencementcylinder injection control section which, when starting the engine basedon the start request, splits fuel injection in an initial cycle to acylinder stopped in the inlet stroke, into a plurality of injections atleast including an injection before engine rotation, to thereby performinjections.
 5. An apparatus according to claim 1, wherein thestart-commencement cylinder injection control section splits the entireinjection amount of the fuel injection of the initial cycle into aplurality of injections before engine rotation, to thereby performinjections.
 6. An apparatus according to claim 1, wherein thestart-commencement cylinder injection control section splits the fuelinjection of the initial cycle into a plurality of injections to therebyperform injections, so that the fuel is at least injected respectivelybefore and after engine rotation.
 7. An apparatus according to claim 6,wherein the start-commencement cylinder injection control sectioncompletes the fuel injections after engine rotation before a timing bywhich an operation of air-fuel mixture suction into the cylinder iscompleted in the inlet stroke.
 8. An apparatus according to claim 7,wherein the start-commencement cylinder injection control section setsinjection intervals of the plurality of fuel injections, based on aremaining period of time in an inlet stroke in a cylinder which has beenstopped in the inlet stroke.
 9. An apparatus according to claim 6,wherein if a remaining period of time of the inlet stroke of a cylinderwhich has been stopped in the inlet stroke is determined as being withina predetermined period of time, the start-commencement cylinderinjection control section injects before engine rotation, instead of thefuel injection of the initial cycle of the cylinder, a fuel injectionamount of the initial cycle, to a cylinder which will undergo an inletstroke after this cylinder.
 10. An apparatus according to claim 6,wherein the internal combustion engine further comprises: a variablevalve actuation mechanism which can at least change a closing timing ofan inlet valve, and when a closing timing of an inlet valve of acylinder which is stopped in the inlet stroke is set to a retarded sideof an inlet bottom dead center by the variable valve actuationmechanism, the start-commencement cylinder injection control sectionsets an injection completion timing of a final injection after enginerotation, to a timing before the inlet bottom dead center.
 11. Anapparatus according to claim 6, wherein the start-commencement cylinderinjection control section controls an injection commencing timing offuel injection after engine rotation, based on an engine rotation speed.12. An apparatus according to claim 1, wherein the start-commencementcylinder injection control section performs control so that an injectionperiod of an earlier fuel injection is made longer than an injectionperiod of a later fuel injection.
 13. An apparatus for controlling fuelinjection of an internal combustion engine for a vehicle comprising: afuel injection valve arranged so as to inject fuel to an inlet port ofeach cylinder of the internal combustion engine; a start requestdetection means which detects a start request of the internal combustionengine; an inlet stroke stopped cylinder determination means whichdetermines a cylinder stopped in an inlet stroke when the internalcombustion engine is stopped; a start request detection means whichdetects a start request of the internal combustion engine; and astart-commencement cylinder injection control means which, when startingthe engine upon detection of the start request, splits fuel injection ofthe initial cycle to the cylinder, which has been determined as beingstopped in the inlet stroke when the internal combustion engine wasstopped before starting, into a plurality of injections at leastincluding an injection before engine rotation, to thereby performinjections.
 14. A method of controlling fuel injection of an internalcombustion engine for a vehicle, the method comprising the steps of:injecting fuel from a fuel injection valve arranged in an inlet port ofeach cylinder of the internal combustion engine; determining a cylinderwhich has been stopped in an inlet stroke when the internal combustionengine is stopped; detecting a start request of the engine; andcontrolling the fuel injection valve so that, when starting the engineupon detection of the start request, fuel injection of the initial cycleto the cylinder, which has been determined as being stopped in the inletstroke when the internal combustion engine was stopped before starting,is split into a plurality of injections at least including an injectionbefore engine rotation, to thereby perform injections.
 15. A methodaccording to claim 14, the method further comprising the steps of:stopping fuel injection when the vehicle stops, to thereby automaticallystop the operation of the internal combustion engine; and in the step ofdetermining a cylinder, determining the cylinder which has been stoppedin the inlet stroke when the internal combustion engine is automaticallystopped; in the step of detecting the start request, detecting a startrequest of the internal combustion engine, which has been automaticallystopped; and in the step of controlling the fuel injection valve, whenstarting the engine upon detection of the start request after theinternal combustion engine has been automatically stopped, splittingfuel injection of the initial cycle to the cylinder, which has beenautomatically stopped in the inlet stroke, into a plurality ofinjections at least including an injection before engine rotation, tothereby perform injections.
 16. A method according to claim 14, themethod further comprising the steps of: detecting an engine temperature;and determining a warm-up completion state in which the detected enginetemperature is greater than or equal to a predetermined temperature, andin the step of controlling the fuel injection valve, when starting theengine upon the start request detection in the determined warm-upcompletion state, splitting fuel injection of the initial cycle to thecylinder, which has been determined as being stopped in the inlet strokewhen the internal combustion engine was stopped before starting, into aplurality of injections at least including an injection before enginerotation, to thereby perform injections.
 17. A method according to claim14, wherein in the step of controlling the fuel injection valve, theentire injection amount of the fuel injection of the initial cycle issplit into a plurality of injections before engine rotation, to therebyperform injections.
 18. A method according to claim 14, wherein in thestep of controlling the fuel injection valve, the fuel injection of theinitial cycle is split into a plurality of injections to thereby performinjections, so that the fuel is at least injected respectively beforeand after engine rotation.
 19. A method according to claim 18, whereinin the step of controlling the fuel injection valve, the fuel injectionsafter engine rotation, are completed before a timing by which anoperation of air-fuel mixture suction into the cylinder is completed inthe inlet stroke.
 20. A method according to claim 18, wherein in thestep of controlling the fuel injection valve, if a remaining period oftime of the inlet stroke of a cylinder which has been stopped in theinlet stroke is determined as being within a predetermined period oftime, the start-commencement cylinder injection control section injectsbefore engine rotation, instead of the fuel injection of the initialcycle of the cylinder, a fuel injection amount of the initial cycle to acylinder which will undergo an inlet stroke after this cylinder.